The present invention relates to an arrangement for feeding fine-particle materials to be separated to an electrostatic free-fall cutter.
Electrostatic methods of separation of fine-particle materials in free-fall cutters have, particularly for dry separation of powdered triboelectrically charged crude potassium salt, great technical importance. The electrostatic separation of crude potassium salt is described in "Chemie, Ingenieur, Technik" 53 (1981), p. 916.
The separation action of the electrostatic free-fall cutter is substantially improved when the free-fall speed of the particles of the material to be separated is braked shortly before the entrance into the electrostatic field. In the German Pat. No. 1,174,273, the braking of the particles of the material to be separated is obtained with an inlet funnel composed of an upper inclined part and a lower part limited by vertical walls. Braking devices formed as open semipipes are arranged in the lower part. The industrial utilization of this arrangement has shown that the material to be separated is braked, but it leaves the inlet funnel in form of individual streams. Since each of these individual streams contains a different quantity of the material to be separated, considerable variations in the flow of the material to be separated take place, which act in a disadvantageous manner on the electrostatic separation.
An arrangement for feeding fine-particle material to be separated to the electrostatic free-fall cutter has also been proposed in which the inlet funnel is formed with braking inserts and inclined walls with lower edges forming a small longitudinal rectangular outlet slot. One of the great walls is inclined to the opposite vertical wall which is provided with inclined downwardly directed guide elements. Finally, a wedge-shaped strip having an upper horizontal surface is arranged at their lower edge and extends into the outlet slot. In this arrangement the material to be separated flows with formation of two fogs out of the arrangement, whereby a greater movement freedom of the particles of the material to be separated in the electric field of the free-fall cutter takes place.
However, it is advisable to further search for solutions which would improve the movement freedom of the particles of the material to be separated in the electric field toward the electrode corresponding to their charge and thereby to further improve the separation output, as compared with the known arrangements.